Cloning and expression of aequorin genes from jellyfish Aequorea and characterization of aequorins activities

Two new aequorin genes, aeqxm and aeqxxm, were isolated from jellyfish Aequorea macrodactyla and Aequorea parva respectively, which are commonly found in the warmer waters on the coastal region of the East China Sea. The DNA sequences of the two genes have no introns and each one contains an ORF of 585 bp in full-length encoding a 195-aa protein. The two genes of aeqxm and aeqxxm share nuclcotide homologies of 80.7% and 85.1% with AEVAQ440X respectively, and the corresponding proteins share amino acid homologies of 84.7% and 84.2% with AEVAQ440X. High amino acid homology was found between apoaeqxm and apoaeqxxm. The two genes were cloned into expression vector pTO-T7 respectively, and the expression yields amounted to 40% of the total protein in E. coli BL21. The activities of the two photoproteins were reconstituted by incubating the expressed apoproteins with coelenterazine f. In the presence of Ca ion, both of the regenerated aeqxm and aeqxxm exhibited an emission peak at the wave length of 470 nm.